Apparatus for coating wire



Nov. 26, 1963 R. R. sT. JEAN 3,112,226

APPARATUS FOR COATING WIRE Filed June 17, 1960 2 Sheets-Sheet 1 ROBERTR. ST. JEAN BY @fd/z ma.,

ATTORNEY Nov. 26, 1963 R. R` sT. JEAN 3,112,226

APPARATUS FOR COATING WIRE Filed June 17, Y1960 2 Sheets-Sheet 2 30 54'y al l2 ATTORNEY United States Patent O 3,112,226 APPARATUS FR CATHNGWERE Robert R. St. Jean, Auburn, Mass., assigner to Worcester AutomaticMachine Company, Worcester, Mass., a corporation of Massachusetts FiledJune 17, 195i), Ser. No. 36,799 7 Ciaims. Cl. 11S-die) This inventionrelates to an apparatus for coa-ting wire. More particularly, theinvention relates to an improved apparatus for coating wire with a thinuniform coating of closely controlled thickness bonded thereto.

There is `a substantial need in the industry for a wire coated with auniform thin metal coating, the coated product having not only anaccurately controlled overall diameter, but the coating being closelycontrolled as to thickness. An example of such wire is tinned or soldercoated copper wire for use as electrical conductors in radios and thelike. The solder coating on such wire is such that junctions betweenwires so coated can be made by heating and pressing the wires -togetherwithout the neces-sity of any additional solder. The best quality wireof this type must have a solder coating of uniform thickness, and thecoating must be free from pin holes and inclusions. In addition, theouter diameter of the wire must be held to very close tolerances ofaccuracy if the product is -to be satisfactory.

It was quite diicult, by use of prior existing coating apparatus andmethods to produce a satisfactory product at `a commercially feasiblerate. Usually the amount of product rejected upon inspection was high,so that not only was the acceptable product markedly increased in costbut -the yamount of waste was unduly high.

The invention has among its objects the provision of a novel apparatusfor coating metal cores of thin gauge with continuous thin uniformcoatings.

A further object of the invention lies in the provision of an improvedapparatus for continuously coating a wire core with a thin accuratemetal coating of la metal having a melting point lower than that of thecore.

Yet another object of the invention lies in the provision of an improvedapparatus for producing a thin metal coating on wire, the product ofsuch apparatus being particularly characterized by the accuracy of thethickness of the coating, the accuracy of the outer diameter of thecoated wire, the perfection of the bond of the coating to the wire core,and the freedom of the coating from pin holes, oxide inclusions, and thelike.

The above and further objects and novel features of the invention willmore fully appear from the following description when the same is readin connection with the accompanying drawings. It is to be expresslyunderstood, however, that the drawings are for the purpose ofillustration only, and are not intended as a definition of the limits ofthe invention.

ln the drawings, wherein like reference characters refer to like partsthroughout the several views,

FIG. 1 is a View in transverse section through a typical coated wiremade by the method and apparatus of the invention;

FIG. 2 is a schematic View partially in section and partially inelevation of a complete wire coating organization, including theimproved apparatus of the invention;

PIG. 3 is an enlarged View in vertical cross section through the metalcoating pot of the apparatus and a portion of the die-forming,protecting, and coatingsmoothing tube associated therewith, certain ofthe parts being shown in elevation;

FIG. 4 is .a fragmentary View on a still greater scale of enlargement ofthe upper end portion of the wire-coating tube associated with thecoating pot; and

iigii Patented Nov. 26, 1963 ice IFIG. 5 is a still further enlargedfragmentary schematic view in vertical axial section through thewirecoating tube in the vicinity of the location where the coating metalon the wire begins to solidify, the section being taken generally alongthe line 5-5 of FIG. 3.

Turning to the drawings, there is shown in FlG. l -a typical coated wire12 having a circular cylindrical core 1i? and a thin solder coating 11bonded thereto. A typical coated wire treated in accordance with theinvention is one having a copper core with la diameter of .030" with auniform solder coating there-about having a thickness of .005. Suchproduct `for some uses must be held `accurateiy to an overall diameterof .040, and must have coating 11 free from pin holes and the 4like andheld within a close tolerance of accuracy as to the thickness.

=It will be appreciated from such requirements that a completelysatisfactory product of this type is hard to achieve.

Turning now to PIG. 2, there is there generally shown a complete wirecoating organization of which the irnproved apparatus of the inventionforms a part. Uncoated wire 10 is fed from a supply reel 14 over a guideroll 1S and thence into an acid cleaning or pickling bath 16 held in apickling pan 17. Upon emerging from pan 17 the wire travels upwardly toa guide roller 19` which is disposed vertically Iabove a coating pot 20.From roller 19 the wire travels downwardly, as shown, into the moltenmetal 24 in the coating pot and thence into the upper end of adie-forming, protecting, and smoothing tube 3o, to be described indetail hereinafter. Upon emerging from the bottom end of tube 36 thethen coated and at least partially cooled wire is led around a furtherguide roller `52, upwardly to roller 54, yand to a take-up reel 56. Thetake-up apparatus is preferably provided with a levelwind device,schematically shown at 57. The described wire traversing system is suchas to pull the wire at a controlled constant speed through the coatingapparatus. Guide rollers 19 and S2 are accurately positioned so as toaid in centering wire in the die-forming and smoothing tube 36.

The structure of the die-forming protecting and smoothing tube of theinvention, and of the metal coating pot in which it is mounted, is shownmore particularly in FIGS. 3 and 4. As there sshown, the lpot 20' has aninner solder cases 21 and an outer heat insulating case 22. T herelatively low melting point coating metal, such as solder 2e, is heldin molten condition at substantially constant temperature, as by athermostatically controlled electric heater 25 of the immersion type.

Mounted on the bottom wall of solder case 21 is an upstanding hollowtubing guide 26. Guide 26 has the lower end thereof protrudingdownwardly through an opening 27 in the bottom of the solder case, anannular flange 29 on member 26 forcibly engaging the annular zone aroundthe opening 27 through the bottom of the oase. Member 26 is held inposition by means of -a check nut 31 disposed beneath the bottom wall ofcase 21 and having screw threaded engagement with the threaded lower end30' of member 26. A thin steel tube 134 is snugly and sealingly engagedwithin the central passage 35 in tubing guide 26. Tube 34 extendsupwardly within member 26 just short of the upper end thereof, andextends downwardly below the lower end of member 26 through the zone 34wherein it is exposed to the atmosphere (FIG. 2) and the further zone34" wherein it lies within a cooling jacket `t2, to be described.

Tube 34 forms an outer strengthening jacket for the inner die-forming,protecting, and smoothing tube proper, designated by the character 36.Tube 36 has a flared upper end 37 which both facilitates the initialentry of a wire thereinto and also tits ywithin the flared upper end 39of passage 35 in member 26, thereby to prevent lthe escape of tube 36from tube 34 and member 26. rthe outer tube 34, with the inner tube 36telescoped therev." hin, is held within member 26 by a packing gland 4lthrough which the assembled tubes extend. Gland 41 is screwed into thecounterbored lower end of member Z6, and serves to compress packingmaterial 4G located within the joint between such members.

As shown in FIG. 2, beyond the location at which the telescoped tubes 34and 36 emerge from the lower end of member 26 they are exposed to theatmosphere at zone 34. From zone 34 the tubes extend into a coolingjacket 42 where they are subjected to a shower of cooling waterdelivered to the upper end of the jacket through a pipe 44. Such watermay be from any source desired and may, if necessary, be controlled asto temperature so that the coating on the coated wire l2 has becomefully solidified by the time the coated Wire emerges from the lower endof tube 36. Ordinarily it is preferred, in the interests of economy inthe use of water, to employ a sump device such as an open topped tank 47in which there is held a substantial quantity of water 49 which hasfallen from the exhaust openings G of the cooling jacket. Water 49 is,in the embodiment shown, continuously supplied to pipe 44 through themedium of pump 45 and the feed pipe 46 leading from the sump to thepump. It is preferred that at least some of the cooling fvvaterdischarged from the cooling jacket shall impinge upon the lower guideroll 52 as shown so as to maintain its temperature Well below themelting point of coating metal i1. In order to make possible the morerapid abstraction of heat from tube 36 and the coated wire 12 passingtherethrough in the zone 34", the thin protective tube 34 is in thatZone provided with a substantial number of small openings 51therethrough, so 4that the cooling water may directly contact the outersurface of inner tube 36 at such locations.

In one preferred embodiment of the invention, the tube 36 is made of ahigh temperature resistant plastic mate- |rial such aspolytetrauoroethylene. Not only does such material substantially retainits strength and durability despite its being heated for long periods tothe temperature of molten solder 4(eg. 350-375 F. for a soldercontaining 2 parts lead and 5 parts of tin), but it displays nonstickingcharacteristics which aid in the passage of the coated producttherethrough and in the smoothing and polishing of the coated product.It is to be understood that, within the scope of the invention, the tube36 may be made of other materials displaying suitable resistance to thetemperatures involved, dimensional stability, and surfacecharacteristics such that the coated wire travels readily therethrough.Among such Iother materials of which tube 36 can be made ispolychlorotriliuoroethylene such as that sold under the trademarks Kel-For that sold under the trademark lFluorothene In accordance with theinvention, the upper end of tube 36 is disposed at a substantial depthl-l below the top of the bath of molten solder 2l. In a preferredembodiment H is maintained at approximately 4 inches. The solder thuspossesses a substantial hydrostatic head at the upper, entrance end oftube 36. It is believed that in its initial passage downwardly throughbath 2l before entering tube 36 the wire core l@ becomes substantiallycompletely wet by the molten solder. The appreciable downward speed ofthe wire core tends to draw molten solder along with it into the tube36. By reason of such motion of the core, as well as capillary actionbecause of the small clearance between the core and the bore 38 throughtube 36, the core tends to center itself in such passage and thus toform a coating of uniform thickness around the core.

It is desired that the coating on the core shall remain substantiallymolten throughout an appreciable length of travel of the wire in orderto penfect the bond between the coating and the core. For this reason itis preferred that the first section 34 of the assembled tubes 36 and beexposed to the atmosphere, as shown, so that the rate of cooling of theproduct in such zone is slow. In the further zone 34", below zone 34,after the coating has become well bonded to the core and the core hasbeen entered in passage 38 in tube 36 by the coating, the coating isthen cooled more rapidly by the cooling jacket 42, functioning as abovedescribed. ln the initial part of zone 34, wherein the coating begins tocongeal but is still plastic, the tube 36 serves to smooth and finallydimension the coating.

The tube 36, as above indicated, functions as a die, as a protectivesleeve, and as a coating-smoothing and dimensioning means. Throughoutthe entire length of travel of the wire from the time it enters coatingbath 21 to the `tin e it emerges from the lower end of tube 36 the wireis completely shielded from the atmosphere, and thus cannot becomeoxidized while the coating is being formed on the core or while the coreis being solidified and smoothed. Such combined actions of the tube 36,plus the fact that the wire is engaged by one continuous smooth surfacethroughout the length of tube 36, are at least in part responsible forthe perfection of the product obtained by use of the invention. In theembodiment shown, the tube 36 snugly embraces inner tube 36 and holdsthe passage 38 therewithin to close tolerances of accuracy as todiameter and straightness. It is to be understood that, in someinstances where the material of which tube 36 possesses suliicientstrength and dimensional stability to maintain its bore diameter andstraightness without reinforcement, tube 34 may be dispensed with.

The apparatus of the invention is further advantageous, because it mayreadily be strung `with Wire 10 at the beginning of a run and may beleft at least temporarily with no wire 1G strung therethrough withoutdamage to any of the parts. As indicated in phantom lines in FIG. 3,wherein the tube 34 is there designated 341, the tube may be raised sothat its upper end 3'7 lies above the top of the bath 24 of moltenmetal. Such raising of the tube may be eflected as by providing abracket, not shown, surrounding the upper end 37 of the tube, suchbracket having a handle which projects upwardly through the molten metal24 and over an upper edge of the pot 20. By pulling on such handle thetube 34 may be raised into the position 341, whereby to facilitate theStringing of wire l@ therethrough, or to prevent the escape of moltenmetal downwardly through the tube when no wire 10 is passingtherethrough.

Although only one embodiment of the invention has been illustrated inthe accompanying drawings and described in the foregoing specification,it is to be especialiy understood that various changes, such as in therelative dimensions of the parts, materials used, and the like, as wellas the suggested manner of use of the apparatus or the invention, may bemade therein without departing from the spirit and scope of theinvention as will now be apparent to those skilled in the art.

What is claimed is:

1. Apparatus for applying and bonding a thin iinpervious coating to acontinuous elongated metal core, comprising a chamber adapted `tocontain a bath of molten coating material, means to maintain the bath atelevated temperature, an elongated generally vertically disposed tubeextending downwardly from the bottom of the chamber, the inner diameterof the tube being substantially uniform throughout its length fromsubstantially its upper to its lower end and equal to the outer diameterof the tinished coated product, the upper end of the tube being open tothe interior of the chamber below the top of the molten material in thechamber, the tube extending a substantial distance below the chamber,means continuously to pull the core down through the molten bath ofcoating material, into the upper end of the tube, and `through the tube,and means to cool the tube at a location below the chamber whereby tosolidify the coating and cool the coated product, the 4tube having aninner surface made of heat resistant plastic material to which thecoating material does not stick during its passage therethrough, theinner surface of the tube consisting of a material selected from thegroup consisting of polytetrailuoroethylene andpolychlorotriuoroethylene.

2. Apparatus as claimed in claim 1, wherein the plastic inner surface ofthe tube is continuous.

3. Apparatus for applying and bonding a thin impervious coating to acontinuous elongated .metal core, comprising a chamber adapted tocontain a bath of molten coating material, means to maintain the bath atelevated temperature, an elongated generally vertically disposed tubeextending downwardly from the bottom of the charnber, the inner diameterof the tube being uniform throughout its length from substantially itsupper toits lower end and equal to the outer diameter of the finishedcoated product, the upper end of the tube being open to the interior ofthe chamber and lying appreciably below the top of lthe molten materialin the chamber, the tube extending a substantial distance below thechamber, means continuously to pull the core down through the moltenbath of coating material, into .the upper end of the tube, and throughthe tube, the exterior of the tube being exposed to the atmosphere for asubstantial distance below the bottom of the chamber, and means to coolthe tube at a location below the exposed zone thereof, whereby tosolidify the coating and cool the coated product, the inner surface ofthe tube being made of heat resistant non-sticking plastic material, theinner surface of the tube consisting of a material selected from thegroup consist-ing of polytetrafluoroethylene andpolychlorotriuoroethylene.

4. Apparatus for lapplying and bonding a thin impervious metal coatingto a continuous elongated metal wire of higher mel-ting point metal,comprising a chamber adapted to contain a bath of molten coating metal,means to maintain such bath at substantially constant elevatedtemperature, an elongated vertically disposed tube extending asubstantial distance downwardly from the bottom of the chamber, theinner diameter `of the tube being substantially uniform throughout thepredominant pant of its length and equal to the outer diameter of thefinished coated product, the upper end of the tube being open to theinterior of the chamber and extending a substantial distance upwardlyinto the bath of molten metal but lying a substantial distance bel-ow`the top of the bath, the tube having a continuous inner surface made ofheat resistance material to which the coating material does not stickduring its passage therethrough, means to guide the wire in its traveldown through the molten metal bath into the upper end of the tube, intothe upper end of the tube, and through 4the tube, the tube having `atirst zone of substantial length below and contiguous tothe `chamberwhich is exposed to the atmosphere, the tube having a second zone ofsubstantial length below the `said irst, exposed zone, and means actingupon said second zone of the tube drastically to cool the tube tosolidify the coating and cool the coated wire, and means below the lowerend of the tube to pull the coated wire 4at substantially constant speedthrough the tube.

S. Apparatus for applying and bonding a thin impervious low meltingpoint metal coating to a continuous elongated cylindrical metal wire `ofhigher melting point metal, comprising a chamber adapted to contain `abath of molten coa-ting metal, means to maintain such bath atsubstantially constant elevated temperature, an elongated verticallydisposed tube extending a substantial distance downwardly from thebottom of the chamber, the inner diameter of the tube beingsubstantially uniform from substantially its upper to its lower end andequal to the outer diameter of the finished coated product, the upperend of the tube being open to the interior of the chamber and extendinga substantial distance upwardly into the bath of molten metal but lyinga substantial distance below the top of the bath, the tube having acontinuous inner LlO surface made of heat-resistant plastic material towhich the coating material does not stick during its passagetherethrough, means to guide the wire in its travel down through themolten metal bath into the upper end of the tube, into the upper end ofthe tube, and through the tube, the tube having -a iirst zone ofsubstantial length below and contiguous to the chamber which is exposedto the atmosphere for a substantial distance below the bottom of thechamber, a cooling jacket surrounding the tube at a second zone ofsubstantial length ofthe tube below such exposed zone thereof, means tosupply the jacket with cooling water and to cause such water to impingeupon the outer surface of the tube, whereby .to solidify the coating andcool the coated wire, and means below the lower end of the tube to pullthe coated wire at substantially constant speed through .the tube.

6. Apparatus -ior applying and bonding a thin impervious metal coatingto a continuous elongated metal wire of higher melting point metal,comprising a chamber adapted to contain a bath of molten `coating metal,means to maintain such bath at substantially constant elevatedtemperature, an elongated vertically disposed tube extending downwardlyfrom the bottom of the chamber, the inner diameter of the tube beingsubstantially uniform throughout the predominant part of its length andequal to the outer diameter of the nished `coated product, the upper endof the tube being7 open to the interior of the chamber and extending asubstantial distance upwardly into the bath of molten metal but lying a`substantial distance below the top of the bath, the tube having acontinuous inner surface made of heat resistant plastic material towhich the coating material does not stick during its passagetherethrough, means to guide and continuously pull the wire atsubstantially constant speed down through the molten metal bath, intothe upper end of the tube, and through the tube, the tube being exposedto the atmosphere for a substantial distance below the bottom of thechamber, and means below such exposed portion of the tube drastically tocool the tube to solidify the coating and cool the coated wire, theinner surface of the tube consisting of a material selected from thegroup consisting of polytetrauoroethylene andpolychlorotritluoroethylene.

7. Apparatus for applying and bonding la thin impervious low meltingpoint metal coa-ting to a continuous elongated cylindrical metal wire ofhigher melting point metal, comprising a chamber adapted to contain abath of molten coating metal, means to maintain such bath atsubstantially constant elevated temperature, an elongated verticallydisposed tube extending downwardly from the bottom of the chamber, theinner diameter of the tube being substantially uniform fromsubstantially its upper to its lower end and equal to the outer diameterof the inished coated product, the upper end of the tube being open tothe in-terior of the chamber and extending a substant-al distanceupwardly into the bath of molten metal but lying a substantial distancebelow the top of the bath, the tube having a continuous inner surfacemade of heatresistant plastic material to which the coating materialdoes not stick during its passage therethrough, means to guide andcontinuously pull the wire rat substantially constant speed down throughthe molten metal bath, into the upper end iot the tube, and through thetube, the tube being exposed to the atmosphere -for a substantialdistance below the bottom of the chamber, a cooling jacket surroundingthe tube below such exposed zone thereof, and means to supply the jacketwith cooling water and to cause such water to impinge upon the outersurface of the tube, whereby to solidify the coating and drasticallycool the coated wire, the inner surface of the tube consisting of amaterial selected from :the group consisting of polytetrauoroethyleneIand polychlorotriiluoroethylene.

(References on following page) 7 References Cited in the le of thispatent 2,543,935 2,608,950 UNITED STATES PATENTS 2,842,329

1,370,800 Egerton Mar. S, 1921 2,386,818 seavey ocr. 16, 1945 5 519,669

5:5 Reynolds Mar. 6, 1951 Bradley Sept. 2, 1952 Brennan July l5, 1958FOREIGN PATENTS Italy Mar. 15, 1955

1. APPARTAUS FOR APPLYING AND BONDING A THIN IMPERVIOUS COATING TO ACONTINUOUS ELONGATED METAL CORE, COMPRISING A CHAMBER ADAPTED TO CONTAINA BATH OF MOLTEN COATING MATERIAL, MEANS TO MAINTAIN THE BATH OFELEVATED TEMPERATURE, AN ELONGATED GENERALLY VERTICALLY DISPOSED TUBEEXTENDING DOWNWARDLY FROM THE BOTTOM OF THE CHAMBER, THE INNER DIAMETEROF THE TUBE BEING SUBSTANTIALLY UNIFORM THROUGHOUT ITS LENGTH FROMSUBSTANTIALLY ITS UPPER TO ITS LOWER END AND EQUAL TO THE OUTER DIAMETEROF THE FINISHED COATED PRODUCT, THE UPPER END OF THE TUBE BEING OPEN TOTHE INTERIOR OF THE CHAMBER BELOW THE TOP OF THE MOLTEN MATERIAL IN THECHAMBER, THE TUBE EXTENDING A SUBSTANTIAL DISTANCE BELOW THE CHAMBER,MEANS CONTINUOUSLY TO PULL THE CORE DOWN THROUGH THE MOLTEN BATH OFCOATING MATERIAL, INTO THE UPPER END OF THE TUBE, AND THROUGH THE TUBE,AND MEANS TO COOL THE TUBE AT A LOCATION BELOW THE CHAMBER WHEREBY TOSOLIDIFY THE COATING AND COOL THE COATED PRODUCTS, THE TUBE HAVING ANINNER SURFACE MADE OF HEAT RESISTANT PLASTIC MATERIAL TO WHICH THECOATING MATERIAL DOES NOT STICK DURING ITS PASSAGE THERETHROUGH, THEINNER SURFACE OF THE TUBE CONSISTING OF A MATERIAL SELECTED FROM THEGROUP CONSISTING OF POLYTETRAFLUOROETHYLENE ANDPOLYCHLOROTRIFLUOROETHYLENE.